tun: fix a crash bug and a memory leak (b09e786b) · Commits · 戴 / test

This patch fixes a crash tun_chr_close -> netdev_run_todo -> tun_free_netdev -> sk_release_kernel -> sock_release -> iput(SOCK_INODE(sock)) introduced by commit The problem is that this socket is embedded in struct tun_struct, it has no inode, iput is called on invalid inode, which modifies invalid memory and optionally causes a crash. sock_release also decrements sockets_in_use, this causes a bug that "sockets: used" field in /proc/*/net/sockstat keeps on decreasing when creating and closing tun devices. This patch introduces a flag SOCK_EXTERNALLY_ALLOCATED that instructs sock_release to not free the inode and not decrement sockets_in_use, fixing both memory corruption and sockets_in_use underflow. It should be backported to 3.3 an 3.4 stabke. Signed-off-by:

Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz> Cc: stable@kernel.org Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/net/tun.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -358,6 +358,8 @@ static void tun_free_netdev(struct net_device *dev)
		{
		struct tun_struct *tun = netdev_priv(dev);

		BUG_ON(!test_bit(SOCK_EXTERNALLY_ALLOCATED, &tun->socket.flags));

		sk_release_kernel(tun->socket.sk);
		}

		@@ -1115,6 +1117,7 @@ static int tun_set_iff(struct net net, struct file file, struct ifreq *ifr)
		tun->flags = flags;
		tun->txflt.count = 0;
		tun->vnet_hdr_sz = sizeof(struct virtio_net_hdr);
		set_bit(SOCK_EXTERNALLY_ALLOCATED, &tun->socket.flags);

		err = -ENOMEM;
		sk = sk_alloc(&init_net, AF_UNSPEC, GFP_KERNEL, &tun_proto);

include/linux/net.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -72,6 +72,7 @@ struct net;
		#define SOCK_NOSPACE 2
		#define SOCK_PASSCRED 3
		#define SOCK_PASSSEC 4
		#define SOCK_EXTERNALLY_ALLOCATED 5

		#ifndef ARCH_HAS_SOCKET_TYPES
		/**

net/socket.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -522,6 +522,9 @@ void sock_release(struct socket *sock)
		if (rcu_dereference_protected(sock->wq, 1)->fasync_list)
		printk(KERN_ERR "sock_release: fasync list not empty!\n");

		if (test_bit(SOCK_EXTERNALLY_ALLOCATED, &sock->flags))
		return;

		this_cpu_sub(sockets_in_use, 1);
		if (!sock->file) {
		iput(SOCK_INODE(sock));

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